Started to collect info into README.md. WIP

Nowhere near ready yet.
Continue describing the concepts and processes.

It's still WIP.
Replaced `load` wit `payload`, for clarity.
Replaced more `load`s wit `payload`, for clarity.
Added some info about interactions with highlights
First pieces
Use Array.isArray, instead of jQuery
Removed test code
Removed unused dependencty
API changes
Next steps
Add searchUntilFirst utility
Make anchoring work
Renamed domMapper to _document
Next steps
Better error reporting
package.json: add license, fix url